a boiling water inside a kettle

How Long is Boiled Water Sterile For?

The length of time boiled water remains sterile depends on the temperature and facilities of where it’s kept and the method used in sterilizing it. For example, water kept at room temperature can remain sterile for up to a day, while water kept in a refrigerator will remain sterile for three days. 

However, according to the CDC, boiled water will remain sterile for drinking for up to six months at room temperature.

Sterilizing is one of the best ways to keep water safe. Often, tap water contains bacteria, pollutants, and pathogens which can be killed by sterilization. While bottled water is safe, it does not qualify as sterile water and will need to be boiled, especially if you plan to use it for mixing powdered infant formula.

Sterile water doesn’t come from a single water source. Instead, lake water, tap water, cold water, and warm water can all become safe drinking water after sterilization. There are several types of sterile water, such as sterile irrigation water, sterile injection water, sterile saline solutions, etc. 

Is Sterile Water the Same as Distilled Water?

a sterile water stored in a measuring glass

Sterile water is not the same as distilled water. 

Sterile water is water free from bacteria, fungi, and spores. In essence, bacteria can’t reproduce in sterile water. On the other hand, distilled water is made through a distillation process and is free from contaminants. 

Also, sterility is a property of water, while distilled water is a type of water produced through a special process. For example, the process of distilling water often involves boiling it first and then distilling it. This means distilled water is sterile, but sterile water isn’t always distilled.

Sterile Water vs. Distilled Water: Which is Better?

Distilled water is generally better, but sterile water has its uses too. Since distilled water has the characteristics of sterile water and more, it’s the obvious choice. 

Besides, distilled water doesn’t even accommodate airborne bacteria — they can’t live in distilled water, even though they may show up in a standard plate count for bacteria. Also, distilled water is virtually free of all chemicals. 

Moreover, distilled water is the best drinking water. It is considered safe water for hydroponic farming, baby formula, hair, plants, irons, and humidifiers. However, the process is way more complicated than sterilizing water. Also, sterilized water is usually used exclusively as irrigation water and injection water. 

How Do I Make Sterile Water?

There are two ways to make sterile water, by chemical or boiling method. We will walk through both below.

Boiling Method 

a boiling water in a pot

This method is fairly easy with the right equipment, and you can make it with these step by step instructions:

Get a Pressure Cooker/Clear Pan

The first basic step is to get a pressure cooker or a clear pan. Pressure cookers are usually better because the temperature can easily rise above the normal boiling point. 

Add Water 

To begin, add filtered water into the pan. You can do this with a carbon filter or an osmosis machine with a micron filter.


Place the water on the stove and bring it to a boil for 20 minutes on medium heat. Ensure the pan is covered throughout. Keep the temperature maintained at about 250°C. 

Leave to Cool

Allow the hot water to cool before using. Then, put the water in an air-tight container and store it in a refrigerator or at room temperature, following CDC guidelines. 

Some believe boiling your water a second time may increase the level of arsenic and other minerals, causing the water to become dangerous for consumption. This is just a myth. Boiling twice will the minerals in the water but, according to the New York State Department of Health, the increase is negligible and has no effect on the body. Therefore, twice or thrice boiled water is safe, but it may not be wise or energy-efficient to reboil water. 

Also, the taste of the water may change slightly, and if you are particularly sensitive, it may give your water a bad taste.

Chemical Method

This alternative method of sterilizing water is convenient when there’s an emergency. It involves adding chlorine bleach to the water to make it pure. Many infant mothers use this to keep their baby’s water clean.

To sterilize using the chemical method, get a clean stainless steel container ready and put water in it. You can add one teaspoon of chlorine bleach for every eight gallons of water. Stir in the chemical thoroughly and leave the water for about thirty minutes. 

After thirty minutes, the odor of the chlorine should come out. When this happens, the water has become sterilized and ready for use. Sanitize your container and air dry the sanitized container before transferring the water into it. Your water may get a chlorine taste from this method.

How Long is Boiled Water Sterile at Room Temperature? 

Boiled water can be stored for up to six months at room temperature. According to the CDC, the water should be boiled to their specifications and stored in sanitized containers. While there’s no specific range for what qualifies as room temperature, most sources put it at 68-70°F. 

The CDC also states that the water should be kept in food-grade containers. The USA Emergency Supply says you should only use buckets that have been used to store food. If the bucket has come into contact with nonfood material, it’s best to avoid it. For example, ice cream containers, bakery bowls, and buckets used in large kitchens or restaurants qualify. 

It’s helpful to label the container with the storage date to keep track of the water’s shelf life. You should also keep it away from direct sunlight. If the room doesn’t have any shade from the sun, you can wrap the container up in black plastic bags. Also, keep it away from toxic chemicals or materials that may be in the room. 

How Long Does Boiled Water Stay Sterile in a Kettle?

a boiling water inside a kettle

Boiled water can stay potted for at least 2-3 days. The timeline can extend past this, just ensure you keep the kettle clean and dry. Then, pour the boiled water into the kettle as soon as it’s removed from the heat. 

The consensus is that sterile water itself can’t be made in a kettle, especially if it has an automatic shutoff. However, you can keep boiled, bacteria-free water in a kettle. You can also make water drinkable by bringing it to a boil once in a kettle. But it’s generally not okay to leave boiled water in a kettle for too long.

Leaving water in a kettle often results in limescale. This shortens the lifespan and weakens the heating performance of a kettle. Besides, using water kept in a kettle for too long may cause your hot beverage to taste off. The same applies if you use an electric kettle.

Boiled water can stay sterile in a thermos or water bottle for up to seven hours. You should keep the temperature of the thermos above 70°F. 

How Long Does Cooled Boiled Water Stay Sterile?

Boiled water kept in the fridge can stay sterile for three days. It’s best to allow the water to cool after boiling before placing it in the fridge. You can keep the water in sterilized bottles with a ring and a cap to prevent contamination.

Even bottled water can only stay in the fridge for up to six days before it loses its taste. 

How Long Does Sterile Water Last Once Opened?

Sterile water can still be used for up to 24 hours once opened. The water will begin to lose its sterility, but it is still usable within that time frame. Just make sure you close it back immediately after each use. Also, keep it in the fridge when not in use. 

Even after 24 hours, you can use the water to irrigate your nose. 

How Long Can You Keep Cooled, Boiled Water for a Baby to Drink? 

You can keep cooled, boiled water for a baby to drink for up to three days. You should keep this water in a sterilized bottle and ensure it is tightly shut. This water can be used for making a bottle of formula or to spoon-feed the baby. However, some moms say they find it safer to boil fresh water each day and cool it. 

A baby under six months who is being fully breastfed doesn’t need water. You can offer babies sips of cooled boiled water, but this should be kept to small quantities until they reach 6 to 12 months. Ensure you sterilize bottle-feeding equipment for your baby for the first 12 months. 

Final Thoughts 

Sterile water can be used for various purposes and is a home necessity, especially for infant parents. You can make your sterile water at home and enjoy contaminants and germ-free water.

How long sterile water lasts depends on where and how it is stored, so be mindful of your environment and note how long you have stored your sterile water. Also, it’s good to keep boiled water at home in case of any emergency. Just be sure to take the proper steps to preserve your water’s condition.

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